happened. there was a lot of fear just naturally out there. and people said, let's get out of here. >> people inside the club begin to run for the stairwell leading down to the front door. >> it was a very tall, steep stairwell. it was not a stairwell that was built to code, and it really was not suitable for the use that it was put to. and they started running down the stairs. and somebody fell, and then somebody fell on top of them, and somebody fell on top of them. and the next thing you know, people were literally stacked 10, 12 feet high. >> we look at a scenario where your life is under threat, where you're looking for means of escape. do you choose the door you came in by, the route that you know, or door number two? >> keith still is a professor in england and specializes in crowd dynamics.